Slot price:null

I have set the slot price in pricing section of the course but still I am not able to book a slot. Whenever I try to book a slot using a student's account; the popup opens with the slot time but with price:null. Meanwhile when I checked the JS error console, I found the following error right after it opens the slot info popup. And if I press the confirm booking; I see the alert box with message "Pricing enabled but no price set for slot." however I am damn sure I have set the slot price in course pricing section.

book:373 Uncaught TypeError: Cannot read property 'getTime' of undefined at book:373 at Array.sort (<anonymous>) at HTMLDocument.<anonymous> (book:372) at t.value (wplms_appointments_booking.js?ver=1.5:1) at r (wplms_appointments_booking.js?ver=1.5:1) at n.l (wplms_appointments_booking.js?ver=1.5:1) at o (wplms_appointments_booking.js?ver=1.5:1) at B.handleSelectEvent (wplms_appointments_booking.js?ver=1.5:1) at o (wplms_appointments_booking.js?ver=1.5:1) at V.handleSelectEvent (wplms_appointments_booking.js?ver=1.5:1) (anonymous) @ book:373 (anonymous) @ book:372 value @ wplms_appointments_booking.js?ver=1.5:1 r @ wplms_appointments_booking.js?ver=1.5:1 l @ wplms_appointments_booking.js?ver=1.5:1 o @ wplms_appointments_booking.js?ver=1.5:1 B.handleSelectEvent @ wplms_appointments_booking.js?ver=1.5:1 o @ wplms_appointments_booking.js?ver=1.5:1 V.handleSelectEvent @ wplms_appointments_booking.js?ver=1.5:1 onClick @ wplms_appointments_booking.js?ver=1.5:1 o @ wplms_appointments_booking.js?ver=1.5:1 invokeGuardedCallback @ wplms_appointments_booking.js?ver=1.5:1 invokeGuardedCallbackAndCatchFirstError @ wplms_appointments_booking.js?ver=1.5:1 c @ wplms_appointments_booking.js?ver=1.5:1 p @ wplms_appointments_booking.js?ver=1.5:1 m @ wplms_appointments_booking.js?ver=1.5:1 d @ wplms_appointments_booking.js?ver=1.5:1 v @ wplms_appointments_booking.js?ver=1.5:1 g @ wplms_appointments_booking.js?ver=1.5:1 We @ wplms_appointments_booking.js?ver=1.5:1 yr @ wplms_appointments_booking.js?ver=1.5:1 Z @ wplms_appointments_booking.js?ver=1.5:1 qe @ wplms_appointments_booking.js?ver=1.5:1 _r @ wplms_appointments_booking.js?ver=1.5:1 ze @ wplms_appointments_booking.js?ver=1.5:1